Tuning fork type relays



April 2, 1963 H. REIFEL ETAL TUNING FORK TYPE RELAYS Filed Dec. 6. 1961l'awenior s: Har'fly RetfeZ, (Lara/a K812840371, 3 W J. WM

uibiba' ney U wd W Paren 3,034,235 r 1 TUNING FORKT IE'REIQAYS I HarryReifel-,.Waltham-, and G'eraldKaron, Randolph, Mass, assignorstojxstevens-Arnqld ;Inc., South Boston; a s a cor o on of Mas a hu sFiled Dec. 6, 1961, Ser. l {o ,'1-57,494'

5 Claims. (Cl. 200-91) This invention relates to electromagneticrelays,and relatesntore particularly toelectrorna'gneticrelays having tuningfork type, vibratory tynes. v I

This invention uses a tuning fork having it's tyne's -and base stampe'djin, one piece from magnetic sheet metal. An electromagnet, has apermanent ma e ole pi m of am h na n'e and m dwa b twee free ends of thetynes and whfch magnenzes the latt r to oppositepolarities. A.C. at theresonant frequency of the tuningfork isapplied to the coil of theelectromagnet, and causes the free ends of the tynes to be alter n eyattracted by and repelled; byithe magnet insynchronism with the appliedA.C. Since the phase, there is less vibration transmitted to a supportthan wherea'single vibratory reed is used. I A,

One of the tynes has a fixed contact on its innersurf c adjacent o ifree and. nd ast al? m st e lirame of the relay, has aresilient contactstrip canti lever supported thereto, with itjs free end oppositefthecontact on the one tyne. As the 'o'ne tynernoves' inwardly fat or nearits resonant irequen'cy, it touches the free end of the resilientcontact, closing a circuit in which the contacts are connected. Theresilient contact hasa resonant frequency much higher than that of; thetuning" fork. This has the advantage that since the resilient contactdoes not load the tyne it touches, the so-called' holdregipn is aminimum. By hold region is meant the increase in band width to whichthe'tynies respond whenthe relay is in operation. It is desired that thetynes respond to a very narrow band of frequencies centered about theirresonant frequency,- but when; loaded by stifr', lfi xed'contacts, theresponse band increases excessively during operation. This has-thedisadvantagethat the tuning fork vibrates and closesits'contacts'at'frequencies outside its desired operating range, and isnot sufiiciently selective.

The construction of the relay is simplified, and its cost is reduced byusing as a frame, a single strap of nonmagnetic material, to the outerend of which the base of the tuning fork is attached, and byconstructing the tuning fork in a single piece from sheet metal. Thestrap has a flange on its inner end which is cemented to a plastic discon the adjacent end of a coil of an electromagnet, which is concentricwith and has a larger diameter than that of the coil. A plug in typebase has a recessed inner end at the other end of the coil, having thesame diameter as the disc. A metal collar having an outside diameterequal to that of the disc and the recessed end of the base, extendsaround the coil with its edges in contact with the disc and base. Abrass shield has a particylindrical outer portion with an open end whichfits snugly around the recess in the collar and the disc and collar, andhas a Patti-cylindrical, inner portion which has spaced-apart segmentswith ends whichcontact the side of the disc which is cemented to theflange. The inner shield portion forces the disc against the collar andthe latter against the base, and the outer shield portion snuglycontacts the outer surfaces of the discs, the collar, and the recessbase portion, securing these components tightly together without thenecessity for screws or bolts.

An object of this invention is to reduce the hold region of a tuningfork type relay.

Other objects of this invention are to simplify and to reduce the costsof tuning fork type relays.

ms vibrate ontofer CC This invention will now he described withreference to the annexed drawings, of which: I 7

FIG. 1 isa side elevation, in 'sectiomof a relay embodying thisinvention, showing the edge of the tuning fork, and the contact side ofthe support strap;

FIG. 2 is a side elevation, with the shield shown in section, of therelay rotated about its axis from the position shown by FIG. 1; 7

FIG. 3 is a side elev ati'onof the relay looking at the side oppositethat shown by FIG. 1", and

FIG. 4 is afragmentary view of the relay, showing an alternative form offixed contact structure.

A strap 10 of non-magnetic metal has a flange 12 on its 'inner end. Atuning fork '13" formed in one piece from ma'gnetiosheet metal, has abase 14 with an extension '15 which is'attached by a screw 16 to theouter end of the strap 10. The tuning fork has spaced-apart tynes 17 and18; The tyne '17 "has a con-tact 19 on its inner surface adjacent to itsfree end. A fixed contact strip 20' of resilient metal, having a higherresonant frequency than the'tuning fork, is cantilever supported by apin 21 in a disc 23 ofinsu-lation fitted in an'opening' in thestrap 10'.The strip 20 has a contact 22 near itsfree end; opposite and normallyspaced'froni' the contact A circular dise 24 of plastic material iscemented on one side to the flange 12, and on its other side to one endof'cylindrical coil 25, to the opposite 'end' of which a smaller,concentric, circular disc'2'6 of plzisticihatefial is cemented. Thediscs 24 and 26 can he ends of apla'stic spool for the coil. The disc 26and the coil 25 have the same diameter. a I a A- circular base 27of'insul'ationis opposite the disc 26', and has socket'p-ins 29, one ofwhich is connected by wire 30 to the pin 21 and through the latter tothe contact strip20, another of which is connected'by wire 31to thestrap 10, and others of which are connected'hy Wires 32 to the ends ofthe winding of'the coil '25. The base 27 has a larger diarneter'thanlthe disc 24, and has an inner, circular, i'eces'sedportion28"Which the sarne diarne ter as that of the disc 24. I v

A 'per'r'rianentirnagnet 35in the formof a rod extends through the coil'25 along its axis, and forms the polpiece of the coil. One end of themagnet 35 extends through the disc 24 and the flange 12 to a positionmidway between the free ends of the tynes 17 and 18.

A parti-cylindrical collar 37 of non-magnetic metal has the sameexternal diameter as that of the disc 24 and the recessed base portion28, extends around the coil 25 with one of its edges in contact with thedisc 24, and its other edge in contact with the base 27 The collar hasspacedapart ends with an opening 39 therebetween.

A shield can 40 of non-magnetic metal, closed at rtS outer end, has aparticylindrical inner portion 41 having an outer diameter equal to thatof the disc 24, with three, equally spaced-apart segments 42 havingaligned inner ends which contact the side of the disc 24 which iscemented to the flange 12. The can 40 has a particylindric-al, outerportion 45 having an inner diameter the same as the outer diameter ofthe collar 37, and the same as that of the disc 24 and the recessed baseportion 28, and has an inner end portion which fits snugly around thedisc 24, the collar 37 and the recessed base portion 28. The can portion45 has an edge thickness equal to the difference between the diameter ofthe base 27 and its recessed portion 28, so that the outer surface ofthe can extends flush with the outer surface of the base 27.

The outer shield portion 45 by fitting snugly around the disc .24, thecollar 37 and the recessed base portion 28, and the inner shield portion41 by pressing the disc 24 against the collar 37, and the latter againstthe base 27, secures these components tightly together, in addition toacting as the usual electrostatic shield.

Two adjacent segments 42 of the inner shield portion have a space 47between their longitudinal edges, which is aligned with the space 39between the ends of the collar 37. The outer shield portion 45 hasspaced-apart longitudinal edges 48 with a space therebetween which iswider than the space 47 but centered therewith. These spaces provideaccess to the wires and their connections.

The fixed contact strap 20 should have a much higher resonant frequencythan that of the tynes 17 and 18 for reducing the hold region, and insomecases, the length and stiifness of the strip 20 may prevent itsresonant frequency from being as high as it should. In such cases, anadditional, much shorter strap 50 of resilient metal is cantileverattached to the strap 20, and its free end is opposite and normallyspaced from the contact 19 on the tyne 17.

In the operation of FIGS. 1-3, A.C. at the resonant frequency of thetynes 17 and 18 is applied through the wires 32 to the ends of thewinding of the coil 25, producing an alternating magnetic field at theinner end of the magnet 36 acting as the polepiece of the coil, causingthe free ends 0c the tynes to be attracted towards and repelled awayfrom the magnet. At the end of its inward swing during each half-cycle,the tyne 17 moves its contact 19 against the fixed contact 22, closing acircuit which is not shown, in which the contacts are connected. Theoperation of FIG. 4 would be the same except that the contact 19 at theend of the inward swing of the tyne 17 would touch the free end of thecontact strip 50.

What is claimed, is:

l. Atuning fork type relay comprising a frame, a tuning fork having itsbase attached to one end of said frame and having its tynes extendingtowards the other end of said frame, a coil of an electromagnet attachedto said other end of said frame opposite and spaced from the free endsof said tynes, said coil having a parmanent magnet polepiece with oneend extending midway between said free ends, a contact surface on theinner surface of one of said tynes, and a fixed contact strip ofresilient metal insulatedly attached at one end to said frame betweensaid tynes and having a contact surface at its other end extending intothe space between said tynes opposite and normally spaced from saidfirst mentioned contact surface.

2. A tuning fork type relay comprising a frame, a tuning fork having itsbase attached to one end of said frame and having its tynes extendingtowards the other end of said frame, said other end ofsaid frame havinga flange thereon, a plastic disc cemented to said flange, a coil of anelectromagnet supported by said disc, said coil having a polepiece withone end extending midway between the free ends of said tynes, a contactsurface on the inner surface of one of said tynes, and a fixed contactstrip of resilient metal insulatedly attached at one end to said framebetween said tynes and having a contact surface at its other endopposite and normally spaced from said first mentioned surface.

3. A tuning fork type relay comprising a frame having a flange at oneend, a tuning fork having its base attached to the other end of saidframe and having its tynes ex tending towards said one end, a circular,plastic disc cemented to said flange, a cylindrical coil of anelectromagnet supported by said disc, said coil having a polepiece withone end extending through said disc and flange midway between the freeends of said tynes, a contact i strip surface on the inner surface ofone of said tynes, a fixed contact of resilient metal insulatedlyattached at one end to said frame bet-ween said tynes and having acontact surface at its other end opposite and normally spaced from saidfirst mentioned surfaces, a circular base having contact pins connectedto said frame, said fixed contact and to the ends of the winding of saidcoil, at the other end of said coil, and a collar around said coil incontact with said disc and base.

4. A tuning fork type relay as claimed in claim 3.,in which said collarhas an outer diameter the same as that of said disc, in which said "basehas a recessed inner edge having the same diameter as that of said disc,and in which a shield can is provided which has an outer portion incontact with said disc, said collar and said recessed edge of said base.

' 5. A tuning fork type relay as claimed in claim 4 in which said canhas an inner portion with an end which contacts the side of said discwhich is cemented to said flange.

References Cited in the file of this patent UNITED STATES PATENTSEannarino Nov. 1, 1949

1. A TUNING FORK TYPE RELAY COMPRISING A FRAME, A TUNING FORK HAVING ITSBASE ATTACHED TO ONE END OF SAID FRAME AND HAVING ITS TYNES EXTENDINGTOWARDS THE OTHER END OF SAID FRAME, A COIL OF AN ELECTROMAGNET ATTACHEDTO SAID OTHER END OF SAID FRAME OPPOSITE AND SPACED FROM THE FREE ENDSOF SAID TYNES, SAID COIL HAVING A PARMANENT MAGNET POLEPIECE WITH ONEEND EXTENDING MIDWAY BETWEEN SAID FREE ENDS, A CONTACT SURFACE ON THEINNER SURFACE OF ONE OF SAID TYNES, AND A FIXED CONTACT STRIP OFRESILIENT METAL INSULATEDLY ATTACHED AT ONE END TO SAID